This application relates to optical semiconductor devices and methods of manufacturing such optical semiconductor devices, including light-emitting devices.
In recent years, nitride semiconductors containing nitrogen as a group V element have been in the limelight in the field of semiconductor light-emitting devices utilizing pn junction, such as light-emitting diodes and laser diodes, and have been researched and developed. The nitride semiconductors such as AN, GaN, and InN are direct gap semiconductors. Moreover, nitride semiconductors of ternary mixed crystal type or quaternary mixed crystal type can emit light from infrared light to deep UV light by appropriately setting composition to vary a band gap (a band gap Eg can be varied from 0.75 eV to 6.2 eV).
Furthermore, a semiconductor light-emitting device which uses an AlGaInN quaternary mixed crystal as a material for a light-emitting layer and emits light in an UV region has received attention as exemplified by the disclosure of Japanese Patent Application Publication No. Hei 9-64477. Although an AlGaInN layer includes In, an emission peak wavelength can be set in a wavelength band of 360 nm or less and reportedly, its internal quantum efficiency can be improved to a similar extent to that of an InGaN layer.